The present invention relates to a surface acoustic wave device, and more particularly, to a substrate cut angle which is suitable for a single crystal piezo-electric substrate to which an additive is added to constitute a surface acoustic wave device.
A surface acoustic wave device (hereinafter called the “SAW device”) which utilizes a surface acoustic wave (SAW) generated by a piezo-electric effect is widely applied to portable telephones and other electronic equipment as an electronic device such as a filter, a resonator and the like, because of its small size and light weight as well as high reliability.
The SAW device generally comprises a first electrode which is applied with a high frequency signal to excite a surface acoustic wave, a second electrode which receives the surface acoustic wave propagated thereto after excited by the first electrode, and converts the surface acoustic wave again to an electric signal to extract a signal at a particular frequency, and a piezo-electric substrate on which the first and second electrodes are formed. The SAW device can form part of a signal processing device for extracting a signal at a particular frequency, such as a filter, a resonator, a duplexer and the like.
A variety of proposals have also been made for an angle at which a used piezo-electric substrate is cut such that a resulting filter or resonator exhibits optimal electric characteristics, for example, in JP-A-2004-507960 and JP-A-9-167936.